Gripping device for automatic lathes



mm vm M A. BECHLER GRIFFING DEVICE FOR AUTOMATIC LATHES Filed Sept. 25, 1946 June 15, 1948.

km W wmw R E N C n V MM m mm m w m a A. ww QN Patented June 15, 1948 111v.rm:,1) {PATENT 'QFFICE pAndr =Bechler, Moutier, Switzerland Application September'23; 1946; Serial =N 056985812 Imswitzerland 'June l'l, 1946 4 Claims. 1 automaticwlathes gripping deviceeare used which cou'plethe bar 'from :'which the: piecesxare for-med l to the headstock rspindlerby'rmeans-of a split-collet type of chuck rwith conical' head; engagingwith a"correspondingconical. bore in the nose of' 'the said spindle, the "gripping :being by a relative displacement ofrtheazspindle: and the chuck, causing the jaws to close.

The relative displacement in question is ;trans "mitted by a' dog clutch'gripping device mounted concentrically on the headstock spindle, whose axial movement, given by the lathe camxshift, acts 'onlevers pivoted in a-sleeve,rfulcruming. on a fixedv point on the: headstock spindle; and consequentlycausingan axial movement of the said sleeve. This sleeve has one or morez-dogsinserting through the "wall of the headstockwspindle .into a spindle acting'dire'ctly on the splitcollet chuck.

'Such: devices are" known. They :possess the advantage of holding the bar perfectly solid with the headstock spindle, if the bar has a diameter corresponding exactly tothe diameter ionwhich thechuck has been adjusted. -In practice, hewever, it is hardly-possible to 'obtainxbars-of absolutely uniform outside diameter; thesamount of tolerance allowed in material found. onthe "market is ofa magnitude of several tenthsof a millimetre and such differences-are quitesuffi- .cient to infiuencethe correctgripping. of-the bar, so-that should the latter undergosgreat strain on turning, slipping will result, giving risetounaccurate work.

- Thedripping device according to -the.. present inventionis of the sametype asthe onedescribed -above. ."Il'r ischaracterised by therfact, that it @comprises at least onetinclined surface interposed -wbetween two parts of. a series. of organsoloetween the fixed pointon-which thelevers fulcrumrand "themsleeve in which the latter. are. pivoted and 1 whose position is determined (by a .feelertdevice under the-influence oftthe diameter. of ,the bar.

With the deviceaccording to this invention, the --:initial position'of. the gripping. mechanism can be varied in'relation' to thediameter of the bar, so that-perfect regularityinhthe.action of the levers is obtained, forithe latter .will always be actuated .from the. point atwhich the split collet chuck holds the bar lightly to'the' extent corresponding to the adjustment of a braking device.

The attached drawing shows, byway or example, and to'the extent necessary -*to 'theunderstanding of the invention, a gripping device for automatic lathes according *to the present invention.

2 Fig. 1; is'r a. longitudinal? section of the device fthroughv theheadstock spindle. axis, the-driving wmechanism being left out.

- :Fig. '2 isca cross sectionallview of the same 5 along; the li-nes I.II-- :-II I- -in 1 ig. 1.

3 Fig, 3; represents the, evolution of two circular warts of thesame, of which therewill ,be question laterron.

-.-Fig.-- 42 is--a-,.cross sectional .view of the device 13:1011? the ,line IVQIVtinFig. 1.

Fig; 5v isanwend viewofithesame and Fig.z.6;-a plan view. of: a portion of. certain, parts shown in section in Fig. 1.

1 The hollow & live spindle i0 of the automatic 15 lathe, -a portion l-onl-y 3 0f which is represented, turns inthebearings- H. and 1.2. The detachable THOSE-l3 ofgthe live spindle :istconed. l4 internally for reception;of -ansplit.colletztype .of chuck l5 xseen intend-on view insFig. 5 and=- opened .and eclosed -sunder theainfiuence of axial movement transmitted to it,.-by ra tightening spindle l6, slid- ;ring-zwithin .therlivetspindle l0 (and having an internalc thread I! ,to' take the interchangeable l-collet. tor-:barswof different. size.

A; spring? l8+ islinterposedi betweenla shoulder a in the hollowv liveI spindleqand-thesaid tightening spindle l ii /with the ,-pur,pose of pushing the collet out in iorder to open, it. The tightening spindle :is providedtwithga recess. 19 in .its side in. which v the dogifl. oi the: sleeve 2 Lmounted, coaxially on the live :spindle l0 and .on which .are pivoted at 480 toeaohothenthe lever, 22 is inserted. These ,1evers,-,are;-pivoted., at, .23, and,.carry rollersf24 at Aisha-extremity ofoneoftheirarms. ,These rollers as-cooperate. withbev'elled.v faces 25. provided at the front end .of thacontrolling sleeve 26 of the dog- -,-tolut.ch gripping device. .,'I his sleeveis moreover iformed by .a; uide-.wheel 21. with circular groove ainvwhich a forked controlling lever, which is not 40 represented,- rides, w ith a. view to sliding the said 1 sleeyecalong; the; live spindle. ,l 0, ,thus operating theidogeclutch gripping,device.

- .?A bevel-wheel, 281integral. with ,an ordinary rpinion.29.-is: pivoted in a recess in the tightening sleeveil. tT-he-.pini on ,29.,meshes with teeth 3t cutv-inc-thet ,plunger,v shaped tdogr3l of the dog- @clutch, ,made to v-coOllera,te. witha ,braking device .1 32, described .furthendown. The, bevel-wheel 28 nieshesawith teethl cut attheperiphery in one of-,.-the iacesofiza,ringi33 which can ,be made to turn on the-live, spindle ,l 0, and to cooperate, with a-second-pring 36rwhose periphery is a portion of alqsphere ,thr0, 1 1gh the medium of helicoidal surriaces 343- 35 proyidedyon thesaid rings, respecmtive1y. Thelatterringjfi is adjusted in a spherical recess of a third ring 31 fixed to the live spindle it in some known manner. This ring 31 forms the fixed point referred to in the first claim.

The evolution of the rings 33 and 3B is shown: in Fig. 3. It can be seen that the relative movement of these parts by turning the bevel-wheel 28 causes the helicoidal surfaces to slide one over the other with the result that the rings 33 and 33 are forced apart, thus increasing the distance separating the fixed ring 31 and the point o contact of the lever 22. Now, this point of contact stands in mechanical relationto' a series of organs, i. e., the rings 31, 36 and 33 and an intermediary piece 39, in such a way that when the rollers 24'of the levers 22 are broughtjnearer the live spindle I by the action of the bevelledfaces 25, the said levers fulcruming medianly on, the ring 31 will displace the sleeve 2| in the direction ofthe arrow-head B. V

p The plunger 3| passes through the box 32 of the braking device containing two conical split bushes 40 and 4| and a helical spring 42 which constantly presses thelatter on to the cylindrical surface of the plunger 3|. "The pressure of the spring canbe regulated by means of a gland A3 in which one end of the said spring is lodged. The position of this gland is fixed by means of a lock nut 5|. The spring is compressed by screwing up the gland. Consequently, the conical split bushes 40. and M will close m'ore tightly about the plunger 3|, thus braking'any motion imparted to the latter.

Thedevice represented functions as follows: The drawing shows the device in the gripping position with the barlof work which is not represented, made solid with the collet chuck [5. When the collet is open, the position of the levers is shown by dotted lines; the rollers are not yet in a position to be acted-upon by-the bevelled ,faces 'of the controlling sleeve 26 and the point of contact 38 is, therefore, not touching the intermediary piece 39,,so that the tightening sleeve 2| is free. As a result, thespring l8 pushes the tightening spindle IS with collet l5 forward, dis-' engaging the collet-head from its'coned-seating I4 and consequently loosening the bar.

Insimilar devices generally in use, the bar is freedin this very position by a back movement of the bearings carrying the live spindle l0 and bytheblockage of the end of the said bar.

To grip, the bar in the chuck, the forked controlling lever arm, which is not represented, directedby the lathe camshaft, pushes the controlling sleeve 26in the direction of the arrow head 45. Before the rollers come into actual contact with the bevelled faces 25 of the controlling sleeve, the latter transmits its motion to r the plunger which, owing to the friction between the parts 40, Al, and the latter, is coupled to it. The plunger, therefore, actsthrough the medium of its teeth 30,.the pinion 29, the bevel-wheel 28, on the ring 33,, with the result'that' a relative rotative displacement ofthe helicoidal surfaces 34 and .35 is,

and 33. Thering 33 bearing onthe opposite I 2|), pulls the the split collet chuck likespindle, .thus causing the jaws of the chuck to 7 close on the bar. Once theinitial adjustment'of the chuck with respect to the diameter ofthe will be movedtowards the spindle. On coming into contact with the intermediary piece 39 at the point of contact 38, the fulcrums of the levers change their positions from the pivots 23 to the points of contact, 38, so that the force is transmitted to the controlling sleeve 2| in the direction of its axis, conveying it through the medium of the dogs 20 to the split collet chuck [5, closing it effectively on the bar of work.

, It follows from the foregoing description that the levers come into effective operation at the point where the jaws of the chuck are already in contact with the bar, for the gripping in variably takes place'under the same influence of the rollers moving through a constant diametrical course, whatever may be the initial position of the chuck; The gripping is always effective and no undesirable slipping is to be feared.

What I claim is: c 1. In a grippingdevice for automatic lathes, a live spindle, awork-grippingcollet mounted on --said live spindle, a tightening tube flxedto said produced, which has the effect of increasing the distance separating the rings 36 collet and slidably arranged in said live spindle, a tightening member slidably mounted on said live spindle, a means establishing .drive'connection between said tightening tube and said tightening member, levers pivoted on said tightening member to abut on saidlive spindle, a control member slidably mounted on said live spindle to control said levers, an adjustable member abutting on said live spindle and on said tightening member to displace the latter on being adjusted,

' driving'means' in driving connection with said adjustable member to adjust the latter for displacement of said tightening member along said live spindle, and a coupling designed to establish automatically driving connection between said control member and saiddriving means to reach a certain displacement of said tightening member by means of said adjustable members before said collet is tightened by said levers.

2. In a gripping device for automatic lathes, a

live spindle comprising a bearing surface-,a workgripping collet mounted on said live spindle, a tightening tube fixed to said collet and slidably arranged in said live spindle, a tightening member slidably mounted on said live spindle, a means establishing drive connection between 1 said tightening tube and said tightening member,

levers pivoted on said tightening member to abut on said live spindle, a control member slidably mounted on said live spindle to control said levers, a rotatable ring traversed by said live spindle, abutting on said tightening memberand having an inclined surface abutting on said bearing surface to displace, said tightening member 'onsaid rotatable ring being rotated, driving means in driving connection with saidrotatable ring to rotate the latter for displacement of said tightening member along said live spindle, and a coupling designed to establish automaticallydriving connection between said control member and said driving means to reach a certaindisplacement of said tightening member by means of said rotatable ring before said collet is tightened by said levers.

3. In a gripping device for automatic lathes, a

live spindle comprising a bearing surface, a workgripping collet mounted on said live spindle, a tightening tube fixed to said collet and slidably arranged in said live spindle, a tightening member slidably mounted on said live spindle, a means establishing drive connection between said tightening tube and said tightening member, levers pivoted on said tightening member to abut on said live spindle, a control member slidably mounted on said live spindle to control said levers, a rotatable ring traversed by said live spindle, abutting on said tightening member and having a toothing and an inclined surface abutting no said bearing surface to displace said tightening member on said rotatable ring being rotated, a first gear wheel mounted on said tightening member and engaging said toothing, a second gear wheel coupled with said first gear wheel, a toothed plunger meshing with said second gear Wheel, and an adjustable brake device fixed to said control member and engaging said plunger so as to establish driving connection between said control member and said second gear wheel to reach a certain displacement of said tightening member by means of said rotatable ring before said collet is tightened by said levers.

4. In a gripping device for automatic lathes, a live spindle comprising a bearing surface, a workgripping collet mounted on said live spindle, a tightening tube fixed to said collect and slidably arranged in said live spindle, a tightening member slidably mounted on said live spindle, a means establishing drive connection between said tightening tube and said tightening member, levers pivoted on said tightening member to abut on said live spindle, a control member slidably mounted on said live spindle to control said levers, a rotatable ring traversed by said live spindle, abutting on said tightening member and having a toothing andan inclined surface abutting on said bearing surface to displace said tightening member on said rotatable ring being rotated, a first gear wheel mounted on said tightening member and engaging said toothing, a second gear wheel coupled with said first gear wheel, a toothed plunger meshing with said second gear wheel, and a brake device fixed to said control member, comprising bushes, a spring, pressing said bushes against said plunger so as to establish driving connection between said control member and said second gear wheel to reach a certain displacement of said tightening member b means of said rotatable ring before said collet is tightened by said levers, and an adjustable gland receiving said spring for regulation of the pressure of said spring.

ANDRE: BECHLER.

REFERENCES CITED The following references are of record in the file of this patent: 

